1. Field of the Invention
The present invention relates to a photographic film, more particularly, it relates to a photographic film which comprises a specific base film layer and photosensitive layer, and is light and excellent in mechanical properties and further has good dimensional stability.
2. Description of the Related Arts
Hitherto, as base films of photographic film, a film of cellulose polymer, a film of polyester, a film of polystyrene having an atactic configuration and the like have been used. Particularly, as bases of films other then rolled films, polyester films excellent in dynamic properties and well-balanced in other properties have been used.
However, a film of cellulose polymer is produced by wet method, resulting in high cost and insufficient mechanical strength. On the other hand, polyester film has some defects. For example, it has high specific gravity and is easily affected by moisture. Accordingly, when it is dried at high temperature while containing moisture, it may be degraded by hydrolysis. When it is used around room temperature, dimensional change attributable to moisture change may occur (moisture expansion coefficient: 1 to 2.times.10.sup.-5 /%RH). Therefore, improvement has been expected in the application wherein accuracy is required, for example, as a master film. Films of polystyrene having an atactic configuration are excellent in transparency, moisture dimensional stability, water absorption and the like, but inferior in heat resistance and mechanical properties.
As mentioned above, the conventionally used base films have various problems, and properties of photographic films obtained from them are not always satisfactory.
The present inventors have studied intensively to develop photographic film with better properties. As the result, it has been found that a styrene polymer having a syndiotactic configuration or a composition thereof has markedly lower moisture expansion coefficient than the conventional heat resistant resin, and is suitable as a raw material for photographic film. Further, it has been found that the above object may be achieved by photographic film using a film with a specific thickness, haze and moisture expansion coefficient as a base film. The present invention has been attained based on such findings.